Buy Now button is tiny

Using marketpress 3.1.
When I have the product set to "Digital Download", the product page displays a nice big "Buy Now" button. (screenshot attached).

When I have the product set to "External/Affiliate Link", the product page displays a tiny little "Buy Now" link. (screenshot attached).

Please tell me where to change the code so that the product page displays a nice big "Buy Now" button when I have the product set to "External/Affiliate Link"

thank you!